Delineation of buried stream channels using geophysical techniques
- Authors: Biedler, Murray W
- Date: 1994
- Subjects: Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4823 , http://hdl.handle.net/10962/d1005498 , Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Description: This study sets out to evaluate the use of geophysical methods for delineating buried stream channels, which can act as zones of preferential flow within a less hydraulically conductive aquifer. This information is important for gaining an understanding of flow dynamics of alluvial systems. The most reliable method of delineating the dimensions of aquifers is by drilling, which is an expensive proposition and is best preceded by a preliminary geophysical study to help define target zones for a drilling program. The study area is located adjacent to the Coerney River in the Sundays River Valley. Geologically it consists of approximately 5 metres of alluvial fines, covering 3 metres of coarse cobbles and boulders, all underlain by alternating siltstone and sandstone beds of indeterminate thickness. Throughout the area the water is very shallow at approximately 2 metres depth and the groundwater tends to be very saline. An air photo study revealed an old oxbow channel that had been covered over by subsequent agricultural land use. The geophysical methods available for the study were portable seismic refraction, electrical resistivity and electromagnetics. Preliminary field tests clearly showed that seismics did not produce valid results. The methods of electrical resistivity and electromagnetics produced good data and were subjected to further assessment. A grid was surveyed over the study area and both geophysical methods were applied at regularly spaced stations. Soil samples were taken over the same survey grid and analyzed for electrical conductivity in a soils laboratory. The results were compared to the geophysical data in an attempt to quantify the relationship between geophysical response and soil salinity. The data from the electromagnetic survey showed areas of low electrical conductivity which was a possible indication of zones of preferential groundwater flow. A transect of boreholes was drilled over selected electrical conductivity lows and successfully intersected the buried stream channel. A comparison of the borehole logs with the layered earth models from the Vertical Electrical Soundings indicated that the electrical resistivity method was not responding to the features of the buried stream channel and the cobblestone layer. This proved the electromagnetic method to be more valuable for this particular study
- Full Text:
The exploration and evaluation of groundwater units in the Van Rynevelds Pass Dam Basin, north of Graaff-Reinet, Cape Province
- Authors: Woodford, A C
- Date: 1989 , 2013-08-30
- Subjects: Aquifers -- South Africa -- Graaff-Reinet , Hydrogeology -- South Africa , Groundwater -- South Africa -- Graaff-Reinet
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4880 , http://hdl.handle.net/10962/d1013275
- Description: This thesis deals with a groundwater investigation conducted in the Van Rynevelds Pass Dam basin, north of Graaff-Reinet, in the Cape Province. The objective of the study was to assess the groundwater potential of the basin in terms of its development and exploitation as a municipal supply. In order to achieve this objective, fieldwork was carried out involving a hydrocensus, geological/geophysical mapping, drilling, aquifer testing and hydrochemical sampling. The fieldwork was conducted during the period January 1983 to February 1984. The investigation revealed that the most significant ground water occurrence in the study area is an alluvial/weathered bedrock aquifer (Graaff-Reinet aquifer ) . The volume of ground water stored in the Graaff-Reinet aquifer is in the order of 27 x 10⁶ m³, while its exploitation potential is conservatively estimated at 9 300 m³/day. However, the quality of this water is poor and should be blended with dam water or better quality groundwater. Two minor fractured aquifer units were also identified.
- Full Text:
A hydrogeological assessment of the Uitenhage-Kuils River area, Cape Province, South Africa
- Authors: Bush, Richard Alan
- Date: 1987
- Subjects: Aquifers -- South Africa , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4801 , http://hdl.handle.net/10962/d1001901 , Aquifers -- South Africa , Hydrogeology -- South Africa
- Full Text:
The exploration and evaluation of groundwater units south and west of Graaf-Reinet, Cape Province, South Africa
- Authors: Parsons, Roger Paul
- Date: 1987 , 2013-04-18
- Subjects: Hydrogeology -- South Africa , Aquifers -- South Africa -- Graaff-Reinet , Groundwater -- South Africa -- Graaff-Reinet
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4865 , http://hdl.handle.net/10962/d1007351 , Hydrogeology -- South Africa , Aquifers -- South Africa -- Graaff-Reinet , Groundwater -- South Africa -- Graaff-Reinet
- Description: The investigation reported in the thesis concerns an area south and west of Graaff-Reinet, in the Cape Province. The research projec t identified the existence of four groundwater units. The aquifers predominantly occur in Beaufort Group sediments and the boundary of each unit is formed by dolerite intrusives or with topographical highs. The objective of the study was to quantitatively assess these units in terms of both quantity and quality for possible future development as a municipal supply for Graaff-Reinet. In order to achieve the objective, fieldwork was carried out involving a hydrocensus, geological mapping, drilling, aquifer testing and hydrochemical sampling. The analysis of these data revealed that the Sundays and Kamdeboo aquifer units are unsuitable for further development. The Moordenaars and Swart units, both of which produce good quality water, have a combined exploitation potential in the order of 30 000 m³ /d. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text: